Confinement effect on the bond behaviour of beams under static and repeated loading

This paper examines the effect of confinement from the stirrups and supports on the bond behaviour of the steel to concrete interface in reinforced concrete beams. The test variables included the corrosion level of the tensile reinforcement, the anchorage length, the stirrup spacing and the fatigue load range. It was found that decreasing the stirrup spacing from 150 mm to 75 mm increased the bond capacity and changed the mode of failure under monotonic loading from splitting to pullout. The beams with the first stirrup spacing when tested under repeated loading failed by bond fatigue while the beams with the second stirrup spacing failed by flexure at the end of a debonded region that started from the support. The failure mechanism is discussed for each case.